Field of the Invention
The present invention relates to an internal combustion engine and more specifically to an arrangement which permits the compression ratio of said engine to be under an operator's control.
A number of methods have been patented for the purpose of varying piston-engine compression ratios during operation. One method is typified by U.S. Pat. No. 4,286,552 (Tsutsumi). This patent teaches a secondary piston in the cylinder head of the engine which is retracted to increase head space volume (lower compression ratio) and extended to raise compression ratio. Many forms of this idea exist, varying in the means of control, but all requiring highly specialized cylinder head construction.
A second class of compression ratio control is shown in U.S. Pat. No. 4,469,055 (Caswell). This patent teaches a multi-element piston in which the upper and outer element is spaced outwardly through the addition of fluid into a cavity formed between two elements of the piston, lengthening it with respect to the wrist pin and raising the compression ratio. This design requires for each piston at least a two-passage flexible line connected from a separate pump to maintain control and fluid circulation for cooling. As pistons move up and down several inches per stroke at 50 to 100 per second, it is seen that this approach may be impractical.
A Japanese Provisional Patent 5,891,340 (Kokai) places an eccentric bearing between the piston and the connecting rod. The eccentric has two positions, for high and low compression, and requires two oil passages drilled through each connecting rod, the crankshaft and all crankpins plus a control valve and hydraulic positioning means in each cylinder.
A large number of patents based on the multi-element piston in various forms have been issued. A common element in these patents is that they are controlled by fluids fed through a drilled crankshaft, crankpins and connecting rods or through an external jointed or flexible fluid tight conduit to their various adjustable pistons. A recent example is U.S. Pat. 4,934,347 (Suga). This piston responds to maximum cylinder pressure and raises compression by fluid inflow when such pressure is below a selected value. Thus the effect of this system is automatic and out of the hands of the operator. A common problem in pistons of this type is that under certain conditions they have little flow through the fluid chamber and overheating can break down the oil therein causing sludge or even coke formations, destroying the piston's function or even the piston itself.
An object of the present invention is to provide a means for controlling an engine's compression ratio without the use of conduits linking the source of the control fluid to the piston.
Another object is to provide for raising the pressure of the control fluid to working within the piston body so that the delivery of control fluid to the piston may take place at low pressures.
Another object is that control of compression ratio may be achieved by control of the volume of fluid flow through fixed jets. Another object is that a continuous flow of control fluid will pass through the piston to provide lubrication and cooling.
Another object is that the invention may be applied to conventional engine designs without alteration of blocks, cylinder heads, crankshafts or connecting rods.